My intuition tells me it's been a long day and typos are creeping in :-)

The last test should have read:

   d=>sub{
                $wait = 0 unless ($wait == abs($wait));
                $wait = -34;
                },
[download]

I thought the results had shot up on my home pc.

      Rate    d    c    b    a
d 3468819/s   --  -8% -10% -13%
c 3780923/s   9%   --  -1%  -5%
b 3834916/s  11%   1%   --  -4%
a 3997317/s  15%   6%   4%   --


and 

       Rate    d    c    b    a
d 3246175/s   --  -8% -15% -17%
c 3526456/s   9%   --  -7%  -9%
b 3799184/s  17%   8%   --  -2%
a 3890565/s  20%  10%   2%   --
[download]

It's still the outright winner - so the questions still stand.